2-D encoded symbol quality assessment

ABSTRACT

An 2-D symbol orientation guide with parallel and spaced right angle guidelines with chevron-like spaces provided therebetween is selectively displayed in plural selected dispositions on a monitor screen as an overlay for the display on the same monitor screen of a 2-D Data Matrix symbol. Manual rotation of the symbol is viewed on the monitor screen as the symbols solid line border is moved into alignment with a guide line at which time the symbol is imaged and its quality graded. Display of the orientation guide in at least five selected rotational dispositions, alignment of the symbol solid line border therewith and imaging and grading of the symbol quality in each such position provides multiple grade scores for averaging into an overall grade score.

BACKGROUND OF THE INVENTION

1. Field of Application

This invention relates to encoded symbology; and, more particularly, toassessing or verifying, the quality of such encoded symbology after ithas been applied to a carrier.

2. Description of the Prior Art

The preferred encoded identification [symbol/symbology] marking for usewith this invention is the two-dimensional (2-D) matrix symbolparticularly the one referred to as “DATA MATRIX”.

One and two dimensional part marks have achieved wide spread acceptancethroughout a wide variety of industries. 2-D matrix symbol/symbology wasdeveloped to overcome many of the deficiencies inherent in thefirst-generation (linear bar codes) and second-generation (stacked barcodes) symbol formats. One of the primary changes was the use of squaresor rectangles as a carrier of data in lieu of the strips of variablewidths used in linear and stacked bar codes. The use of data elements ofknown size and shape makes 2-D matrix codes more versatile. In thematrix code format, black data elements (cells) usually represent abinary “1” and white data elements (cells) usually represent a binary“0”. When these binary values are used together in specific sequences,they represent alphanumeric characters. Matrix symbols can not only beproduced in both square and rectangular format but they can also bescaled in size to fit into an available marking area.

Matrix codes, designed to be applied to any of a variety of articles,parts and products, are described, for example, in U.S. Pat. No.4,939,354 (issued Jul. 3, 1990 to D. G. Priddy, et al.). A matrix codecan store from one to 2335 alphanumeric characters in any language. Anencoding scheme for use with such a symbol has a high degree ofredundancy that permits most marking defects to be overcome. 16-bitcyclic redundancy check and data reconstruction capabilities areincluded in one version; and Reed-Solomon error correction is includedin another. Up to 16 symbols can be concatenated. Error correction andchecking (ECC) code 200 is possible.

The term “DATA MATRIX” has been certified by AIM-USA andAIM-International as a fully public-domain symbology. AIM stands forAutomatic Identification Manufacturers International, Inc. “DATA MATRIX”is a unique machine readable symbol capable of storing a large amount ofinformation within a small physical size. The data matrix symbol allowsfor two-dimensional encoding and decoding. Users are not constrained bythe limitations of a printed symbol. Data matrix symbols are capable ofcarrying 25 to 100 times more information than the typical barcode. Thisrange is directly related to the image quality the printer is capable ofproducing. “DATA MATRIX” codes have the following characteristics: bothheight and width are used to encode data; they work with contrast as lowas 20%; they are readable through 360. degrees. of rotation; they aredesigned to survive harsh industrial environments; such codes are oftenprinted on a substrate such as paper but they can be marked directly onthe surface of a part, without using a paper label or substrate.

Some, systems and devices for reading such one and two dimensionalsymbols begin by determining the orientation of the markings beforetrying to read the symbol. Usually this is done by locating an outerreference bar(s) or a central symbol. Once the orientation of themarking is determined, the marking is read. and several error correctionschemes are available to ensure damage recovery. It has, however, becomeimportant in many applications to verify the quality of the encodedsymbology; including encoded symbology of the “DATA MATRIX” type.

A method for verifying “DATA MATRIX” print quality is shown anddescribed in U.S. Pat. No. 6,244,764 patented on Jun. 12, 2001 to MingLei et al for “Method for Data Matrix Print Quality Verification”. Themethod is described for verifying 2-D encoded symbology print quality onall types of direct part and label marking applications. The describedmethod measures symbol contrast, print growth, axial non-uniformity,unused error correction, and overall grade. In addition to theseparameters, the cell placement accuracy, cell size uniformity, andoverall symbol quality are also measured. The method may also provideother relevant information about the data matrix, such as polarity,symbol size, error correction level, image style, and encoded datastring. However, even the symbol quality indications resulting fromusing the method of this patent does not satisfy some industrial,commercial and/or government symbol quality requirements.

SUMMARY OF THE INVENTION

It is therefore an object of this invention to provide new and novelmethods to assess the quality of encoded symbology.

It is another object of this invention to provide new and novel methodsfor assessing the quality of 2-D encoded symbology.

It is still another object of this invention to provide new and novelmethods to assess the quality of DATA MATRIX type symbology.

It is yet another object of this invention to provide new and novelmethods to assess the quality of DATA MATRIX type symbology appliedeither to a substrate and/or directly to parts and other articles.

It is yet still another object of this invention to provide new andnovel methods to assess the quality of DATA MATRIX type encodedsymbology sufficient to satisfy and comply with industrial, commercialand government standards.

It is yet still another object of this invention to provide new andnovel methods to facilitate multiple positioning of a carrier upon whichthere is a 2-D encoded symbol to assess the quality of the 2-D symbol.

Other objects, features and advantages of the invention in its detailsof construction and arrangement of elements and systems will be seenfrom the above and from the following description of the preferredembodiments when considered in conjunction with the accompanyingdrawings and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a Prior Art schematic of a 2-D encoded symbology of the “DATAMATRIX” type;

FIG. 2 s a schematic arrangement of components for accomplishing the newand novel quality assessment of 2-D symbology and which incorporate theinstant invention;

FIG. 3 is a schematic plan view of the arrangement of some of thecomponents of FIG. 2;

FIG. 4 is a schematic view of a computer monitor screen showing a “DATAMATRIX” type symbol from a carrier in a predetermined disposition withrespect to a symbol orientation guide incorporating the instantinvention;

FIG. 5 is a schematic view of a computer monitor screen, similar to thatof FIG. 4, but showing the “DATA MATRIX” symbol and symbol orientationguide of FIG. 4 in another predetermined disposition;

FIG. 6 is a schematic view of a computer monitor screen, similar to thatof FIGS. 4 & 5 but showing the “DATA MATRIX” symbol and symbolorientation guide of FIGS. 4 & 5 in another predetermined disposition;

FIG. 7 is a schematic view of a computer monitor screen, similar to thatof FIGS. 4-6 but showing the “DATA MATRIX” symbol and symbol orientationguide of FIG. 4-6 in yet another predetermined disposition; and

FIG. 8 is a schematic view of a computer monitor screen, similar to thatof FIGS. 4-7, but showing the “DATA MATRIX” symbol and symbolorientation guide of FIG. 4-7 in still another predetermineddisposition.

DESCRIPTION OF THE INVENTIVE EMBODIMENTS

With reference to FIG. 1, there is generally shown at 20 the basiccomponents of a 2-D (two-dimensional) “DATA MATRIX”-type encoded symbol.Although symbol 20 has been shown with a square configuration, it mayjust as well have any other convenient regular configurations such as arectangle. A border 30 is provided for symbol 20 and includes a firstsolid border 32 that extends in a first direction and a second solidborder 34 that extends in a second direction perpendicular (at a rightangle) to first border 32. Border 30 also includes a first broken border36 that extends in a direction parallel but spaced from first solidborder 32 and a second broken border 38 that extends in a directionparallel but spaced from second solid border 34. A data field 50 isprovided within the space surrounded by border 30.

Conventional computer software for decoding encoded “DATA MATRIX”-typesymbol 20 utilizes solid borders 32, 34 to determine the physical size(length “x” and width “y”) of symbol 20. It should be noted that brokenborders 36, 38 comprise alternate light border cells 60 and dark bordercells 62. Conventional computer software utilizes these broken bordercells 60, 62 to determine the number of rows and columns of cells tothereby determine the number of cells allocated to data field 50. Dataencoding is accomplished by conventional computer software. Data cells66, of symbol 20, are differentiated for encoding purposes in aconventional manner to provide some such cells 66 to include black cellelements representing binary “1” and white cell elements representingbinary “0”. It should be understood, nevertheless, that white cellelements might just as well represent binary “1” while black cellelements represent binary “0”. Contrasting colors other than black andwhite may also be utilized as long as the imaging device and computersoftware can differentiate same between binary “1” representing cellelements and binary “0” representing cell elements. Similarly solidborder cells 32, 34 and broken border cells 36, 38 are thusdifferentiated by contrasting black and white colors; while othercontrasting colors may also be utilized.

In the component arrangement 80 of FIGS. 2 and 3 a support 82 isprovided to receive an article 84 upon which there is disposed a “DATAMATRIX” 2-D encoded symbol such as symbol 20. Article 84 may be anyconventional substrate such as paper, plastic, or the like, or it may bea component, part or other direct marked article. Symbol 20 may beprinted by conventional techniques with available equipment and systemsor it may be directly applied by dot peening, casting, forging or othermethods. Article 84 is positioned on support 82 within the field of viewof a conventionally available camera 90 suitable for symbol imagingpurposes and mounted for selective up (in the direction of arrow A-FIG.2) and down (in the direction of arrow B) movement. A light sensitiveimage sensing array 92 (FIG. 1), which may be of the CCD, CMOS or otherconventionally available and suitable type, is disposed within camera90. A source of illumination 94 is provided to adequately illuminatesymbol 20 for imaging purposes upon light sensitive array 92 of camera90. While illumination source 94 has been shown as comprising a numberof point lights 96, disposed one in each quadrant, such illuminationsource 94 may just as well be a suitable ring light. Illumination source94 might best be selected to provide illumination at 660 nanometerswavelength; but other suitable and appropriate wavelengths may just aswell be selected. A conventionally available computer 100 (FIGS. 2, 4,5, 6, 7 & 8)) is suitably powered and connected or otherwise integratedwith camera 90 to receive images therefrom and display such images upona screen 102 of a monitor 104. Monitor 104 may be part of the computeror a separate component conventionally and suitably connected to thecomputer.

It is important in determining the quality assessment for a 2-D symbol,especially of the “DATA MATRIX” type, to take into consideration theeffects of variations in apparent symbol characteristics. Doing so in anumber of different and selected orientations, relative to the axis ofthe measuring device, of the symbol whose symbol quality is beingassessed, and averaging the obtained quality grades derived from therespective selected symbol orientations, provides for a qualityassessment more suitable for some industrial, commercial and governmentpurposes. Basing the measurement and grading of parameters of areference gray-scale image, the binarised image derived from it and theapplication of the reference decode algorithm to selected defined otherparameters is acceptable for two dimensional symbol quality assessmentand can be accomplished by utilizing a system such as that of U.S. Pat.No. 6,244,764 previously referred to. Quality grading of theseparameters may then be used to provide a relative measure of symbolquality under the measurement conditions used. Each parameter is to bemeasured and a grade on a descending scale of integers from 4 to 0 maybe allocated to it; grade 4 representing the highest quality and grade 0representing failure.

The area within which the above described measurements are to be made isa rectangular area framing the complete symbol 20, including its quietzones. The centre of the inspection area is to be as close aspracticable to the centre of the field of view of camera 90. Theinspection area is not to be the same as the field of view of theverifier, which is to be sufficiently large to include the whole symbol20 plus a 20% extension in at least one of the orientations for symbol20.

In order to provide for the effects of variations in apparent symbolcharacteristics symbol 20 is to be viewed in different orientationsrelative to the axis of the measuring device and to provide a basis foraveraging grades (compass type orientations are utilized to facilitatedescribing the instant method). The quality measurement method describedprovides for five measurements of symbol 20 with an appropriatemeasuring aperture for camera 90 and source of illumination 94. Symbol20 is to be rotated to selected imaging positions in increments of 72degrees, + or −5 degrees, around the optical axis of camera 90 and aquality measurement taken at each position. The first position is to bewith the vertical axis of symbol 20 oriented at 45 degrees, + or −5degrees, to the vertical axis of light sensitive array 92. An overallsymbol grade is to be determined by averaging the quality grades of theindividual images, taken at the selected positions While five selectedimaging positions have been selected it is contemplated that as littleas 4 selected grading positions are possible for an average andadditional grading positions for symbol 20, such as 8 by way of example,may also be used and averaged, depending on industrial, commercialand/or government intentions and requirements.

A 2-D symbology orientation guide 120, incorporating the instantinvention, is provided to facilitate rotational positioning of symbol20, for which the quality is to be assessed, into selected imaging andgrading positions for symbol 20. Guide 120 is provided with a number ofguide lines 130 (FIGS. 4-8) each of which meets at right angles withguide lines 132. Guide lines 130, 132 are selected to be at least aslong as solid borders 32, 34 of symbol 20. and are disposed in paralleland spaced positions with respect to adjacent guide lines. Spaces 140,142 of right angle, chevron-like configuration are formed betweenadjacent guide lines 130, 132. The width of chevron stripes or spaces140, 142 may be selected to be at least as wide as the thickness ofsolid borders 32, 34 of symbol 20 and preferably somewhat wider as willbe explained hereinafter.

As stated above symbol 20 is to be imaged and graded in multiplerotationally orientated positions and the respective assessment gradesfor each such position averaged to provide an overall quality gradeassessment. Orientation guide 120 is, preferably, to be generated onscreen 102 as an overlay for a symbol 20, to be imaged and have itsquality assessed, when such symbol 20 is disposed on support 82 in thefield of view of camera 90, illuminated by illumination source 94 andimaged by camera 90 as symbol 20 is rotated to and through its selectedgrading positions. It should be understood, nevertheless, thatorientation guide 120 may just as well be otherwise provided, such as bya see-through appropriately marked template rotationally and selectivelypositioned over screen 102 and through which symbol 20, appearing onscreen 102, may be positioned and viewed as it is moved to and throughits selected rotational positions.

A first imaging/grading position for a symbol 20 is selected to be at 45degrees. Orientation guide 120 is initially displayed on screen 102 withits guide lines 130 and chevron stripes 140 in their respective 45degree positions, as shown in FIG. 4. An article 84 with its symbol 20is placed on support 82 (FIGS. 1 & 2) illuminated by illumination source94 and in the field of view of camera 90 Article 82 is rotatedcounterclockwise (direction of arrow A FIGS. 1 & 2) and symbol 20appears on screen 102 with orientation guide 120 as an overlay, also onscreen 102, as article 82 and its symbol 20 are so rotated. Rotation ofarticle 82 is continued until solid border 32 of symbol 20 aligns withguide lines 130, (FIG. 4) and/or until its solid border 32 is within achevron space 140. Substantial alignment of solid border 32 of symbol 20within a chevron space 140 may also be acceptable if the chevron spaces140 are selected at a width that permits a canted but substantialalignment of border 32 with a guide line 130 while maintaining the + or−5 degree range. When so aligned camera 90 and its associated imagereader may be activated, by conventional means, to not only image symbol20 but also to subject the image to quality verification and gradingwith the results being appropriately stored for averaging andorientation guide 120 automatically re-oriented to appear on screen 102in its 117 degree overlay position (FIG. 5.).

When the image reader is activated as described above and as herinafterdescribed for all orientation positions of symbol 20, the reader willfirst check that the measured angle of orientation of symbol 20 iswithin the allowable tolerance of angularity; before initiating theverification and grading process. If the orientation of symbol 20 iswithin the allowable tolerance of angularity the verification andgrading process will be initiated. If the orientation of symbol 20 isnot within the allowable tolerance of angularity the user will beprompted to try again.

A second imaging/grading position for a symbol 20 is selected to be at117 degrees; + or −5 degrees. Orientation guide 120 has beenautomatically re-oriented to appear on screen 102 in its 117 degreeposition and as overlay for symbol 20 (FIG. 5.). Article 82 is againrotated counterclockwise (in the direction of arrow A FIGS. 1 & 2) andappears on screen 102 with orientation guide 120 as its overlay, also onscreen 102, as article 82 and its symbol 20 are so rotated. Rotation ofarticle 82 and its symbol 20 is continued and viewed on screen 120 untilsolid border 32 of symbol 20 aligns with guide lines 130 in their 117degree positions and/or until solid border 32 of symbol 20 is within achevron space 140. Here again substantial alignment of solid border 32of symbol 20 within a chevron space 140 is also acceptable as describedabove for the 45 degree positioning. When so aligned camera 90 and itsassociated image reader will be activated, by conventional means, whenthe reader determines that the measured angle of orientation of symbol20 is within the allowable tolerance of angularity as described above,to not only image symbol 20 but also to subject the image of symbol 20to quality verification and grading with the results being appropriatelystored for averaging and orientation guide 120 is automaticallyre-oriented to appear on screen 102 in its 189 degree overlay position(FIG. 6.).

A third imaging/grading position for a symbol 20 is selected to be at189 degrees; + or −5 degrees. Orientation guide 120 has beenautomatically re-oriented to appear on screen 102 in its 189 degreeposition and as overlay for symbol 20 (FIG. 6.). Article 82 is againrotated counterclockwise (in the direction of arrow A FIGS. 1 & 2) andappears on screen 102 with orientation guide 120 as its overlay, also onscreen 102, as article 82 and its symbol 20 are so rotated. Rotation ofarticle 82 and its symbol 20 is continued and viewed on screen 120 untilsolid border 32 of symbol 20 aligns with guide lines 130, in their 189degree positions and/or until solid border 32 of symbol 20 is within achevron space 140. Here again substantial alignment of solid border 32of symbol 20 within a chevron space 140 is also acceptable as describedabove for the 45 and 117 degree positioning. When so aligned camera 90and its associated image reader will be activated, by conventionalmeans, when the reader determines that the measured angle of orientationof symbol 20 is within the allowable tolerance of angularity asdescribed above, to not only image symbol 20 but also to subject theimage of symbol 20 to quality verification and grading with the resultsbeing appropriately stored for averaging and orientation guide 120 isautomatically re-oriented to appear on screen 102 in its 261 degreeoverlay position (FIG. 7).

A fourth imaging/grading position for a symbol 20 is selected to be at261 degrees; + or −5 degrees. Orientation guide 120 has beenautomatically re-oriented to appear on screen 102 in its 261 degreeposition and as overlay for symbol 20 (FIG. 7.). Article 82 is againrotated counterclockwise (in the direction of arrow A FIGS. 1 & 2) andappears on screen 102 with orientation guide 120 as its overlay, also onscreen 102, as article 82 and its symbol 20 are so rotated. Rotation ofarticle 82 and its symbol 20 is continued and viewed on screen 120 untilsolid border 32 of symbol 20 aligns with guide lines 130 in their 261degree positions and/or until solid border 32 of symbol 20 is within achevron space 140. Here again substantial alignment of solid border 32of symbol 20 within a chevron space 140 is also acceptable as describedabove for the 45, 117, and 189 degree positioning. When so alignedcamera 90 and its associated image reader will be activated, byconventional means, when the reader determines that the measured angleof orientation of symbol 20 is within the allowable tolerance ofangularity as described above, to not only image symbol 20 but also tosubject the image of symbol 20 to quality verification and grading withthe results being appropriately stored for averaging and orientationguide 120 is automatically re-oriented to appear on screen 102 in its333 degree overlay position (FIG. 8.).

A fifth imaging/grading position for a symbol 20 is selected to be at333 degrees; + or −5 degrees. Orientation guide 120 has beenautomatically re-oriented to appear on screen 102 in its 261 degreeposition and as overlay for symbol 20 (FIG. 8.). Article 82 is againrotated counterclockwise (in the direction of arrow A FIGS. 1 & 2) andappears on screen 102 with orientation guide 120 as its overlay, also onscreen 102, as article 82 and its symbol 20 are so rotated. Rotation ofarticle 82 and its symbol 20 is continued and viewed on screen 120 untilsolid border 32 of symbol 20 aligns with guide lines 130 in their 333degree positions and/or until solid border 32 of symbol 20 is within achevron space 140. Here again substantial alignment of solid border 32of symbol 20 within a chevron space 140 is also acceptable as describedabove for the 45, 117, 189 and 261 degree positioning. When so alignedcamera 90 and its associated image reader will be activated, byconventional means, when the reader determines that the measured angleof orientation of symbol 20 is within the allowable tolerance ofangularity as described above, to not only image symbol 20 but also tosubject the image of symbol 20 to quality verification and grading withthe results being appropriately stored for averaging.

When all the selected rotative positions have been imaged and graded forsymbol 20 an average grade is determined. And thereafter utilized forthe intended purposes.

There may be situations where symbol 20, or article 82 upon which symbol20 appears, are of a size that is too large for the positioning, imagingand assessment components as described above. In such situations theimaging and assessment components may be mounted for portableutilization. Instead of the article and symbol carried thereby beingrotationally positioned the camera may be rotationally positioned to theselected 45, 117, 169, 261 and 333 degree positions, or whatever otherselected rotational positions are selected. A symbol orientation guide,similar to guide 120, is still to be utilized as on overlay to thesymbol as it appears on the screen and is rotationally positioned asseen on a monitor as described hereinabove. Symbol imaging, verificationand grading will be accomplished as described above with respect to thatof FIGS. 4-8.

It is understood that although there has been shown and describedpreferred embodiments of the invention that various modifications may bemade in the details thereof without departing from the spirit ascomprehended by the following claims.

1. A method of assessing the quality of a 2-D (two dimensional) matrixtype encoded symbol having at least a pair of solid border lines whichmeet at a right angle; including the steps of: (a) positioning the 2-Dmatrix type symbol to be imaged by a light sensitive array; (b)displaying an image of the 2-D matrix type symbol on the monitor screen;(c) providing an orientation guide as an overlay for the monitor screenand the 2-D matrix type symbol when so displayed on the monitor screen;(d) providing said orientation guide with a predetermined number ofsubstantially right angle configured guide lines which are parallel toeach other to provide chevron-like spaces between adjacent guide lines;(e) positioning said orientation guide so that said guide lines andchevron-like spaces are disposed at at least a first rotationaldisposition when viewed on the monitor screen; (f) orienting the 2-Dsymbol so as to be viewed on the monitor screen while being so orientedand with respect to the guide lines on the orientation guide, asdisplayed on the monitor screen, to align a selected solid symbol borderof the 2-D symbol with the guide lines and chevron like-spaces of theorientation guide; (g) imaging, and assessing the grade of the 2-Dsymbol when so aligned; (h) re-orienting the orientation guide and 2-Dsymbol into a selected number of additional rotational positions andimaging and assessing the grade of the symbol at each such rotationalposition; and (i) averaging the grades of all the selected positions. 2.The method of claim 1 including positioning said orientation guide sothat said guide lines and chevron-like spaces are sequentially disposedat a plurality of rotational dispositions when viewed on the monitorscreen and orienting, aligning, imaging and grading the 2-D symbol ateach such position and averaging the respective scores.
 3. The method ofclaim 2 wherein there are five such rotational dispositions.
 4. Themethod of claim 3 including so locating the orientation guide and 2-Dsymbol . at 45 degrees, 117 degrees, 189 degrees, 261 degrees and 333degrees with respect to a vertical axis of the light sensitive array. 5.The method of claim 4 wherein the orientation guide is computergenerated and oriented.
 6. The method of claim 2 wherein there are atleast four such rotational dispositions with each disposition in adifferent quadrant of rotational disposition.
 7. The method of claim 1wherein the 2-D encoded matrix type symbol is a Date Matrix encodedsymbol.
 8. The method of claim 7 wherein the 2-D symbol is manuallyoriented between its selected dispositions and the light sensitive arrayis carried by a camera.
 9. The method of claim 8 further includingproviding an illumination source for illuminating the 2-D symbol atleast while being oriented and imaged.
 10. The method of claim 1including rotationally orienting the light sensitive array while leavingthe 2-D symbol in a stationary disposition and viewing the image of the2-D symbol With respect to the orientation guide in selecteddispositions.